Incursion of meteoric waters into the ductile regime in an active orogen
Incursion of meteoric waters into the ductile regime in an active orogen
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DOI：
10.1016/j.epsl.2014.04.046
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发表时间：
2014-08-01
影响因子：
5.3
通讯作者：
Roberts, Stephen
中科院分区：
文献类型：
--
作者：
Menzies, Catriona D.;Teagle, Damon A. H.;Roberts, Stephen
新西兰阿尔卑斯山断层的快速构造隆起提升了地形、区域地热梯度和脆韧性过渡的深度，并驱动了影响造山带内变形和矿化的流体流动。石英脉的氧和氢稳定同位素、流体包裹体和傅里叶变换红外（FT-IR）分析表明，石英脉形成于不同的深度、温度和变形机制，可确定流体来源和大气沃茨的渗透深度。大多数矿脉是在脆性条件下形成的，其同位素特征（δ O-18（H2O）= 9.0至+8.7 ‰（vsmow），δ D = 73至45 ‰（vsmow））表明岩石逐渐平衡的大气沃茨。两代石英脉的形成时间晚于糜棱叶理，但经历了进一步的韧性变形，因此在脆性到韧性过渡带（>6-8 km深度）下方形成，保存了SD值在84和52%o之间的热液流体，表明形成于大气沃茨水。这些静脉的FT-IR分析显示没有结构氢释放的证据，排除了这作为低SD值的来源。相比之下，这些流体的氧同位素信号几乎与寄主岩石完全平衡（δ O-18（H2O）= +2.3至+8.7千分之一）。这些数据表明，大气沃茨占主导地位的岩石中的流体相，并没有稳定同位素的存在变质流体的沉淀过程中的韧性变形石英脉的要求。这就要求在造山作用期间，大气沃茨渗透到脆性到韧性的过渡带中，并可能渗透到该过渡带之下。(C)2014作者由爱思唯尔公司出版
Rapid tectonic uplift on the Alpine Fault, New Zealand, elevates topography, regional geothermal gradients, and the depth to the brittle ductile transition, and drives fluid flow that influences deformation and mineralisation within the orogen. Oxygen and hydrogen stable isotopes, fluid inclusion and Fourier Transform Infrared (FT-IR) analyses of quartz from veins which formed at a wide range of depths, temperatures and deformation regimes identify fluid sources and the depth of penetration of meteoric waters. Most veins formed under brittle conditions and with isotope signatures (delta O-18(H2O) = 9.0 to +8.7 parts per thousand(vsmow) and delta D = 73 to 45 parts per thousand(vsmow)) indicative of progressively rock-equilibrated meteoric waters. Two generations of quartz veins that post-date mylonitic foliation but endured further ductile deformation, and hence formation below the brittle to ductile transition zone (>6-8 km depth), preserve included hydrothermal fluids with SD values between 84 and 52%o, indicating formation from meteoric waters. FT-IR analyses of these veins show no evidence of structural hydrogen release, precluding this as a source of low SD values. In contrast, the oxygen isotopic signal of these fluids has almost completely equilibrated with host rocks (delta O-18(H2O) = +2.3 to +8.7 parts per thousand). These data show that meteoric waters dominate the fluid phase in the rocks, and there is no stable isotopic requirement for the presence of metamorphic fluids during the precipitation of ductilely deformed quartz veins. This requires the penetration during orogenesis of meteoric waters into and possibly below the brittle to ductile transition zone. (C) 2014 The Authors. Published by Elsevier B.V.